Terminal with insulation piercing ferrule



' Nov. 11,1952 F ,P.ER 2,617,845

TERMINAL WITH INSULATION PIERCING FERRULE Filed Oct. 16, 1947 IN V EN TOR. 64m! A.

Patented Nov. 11, 1952 TERMINAL WITH INSULATION PIERCI NG FERRULE Frank L. Pierce, Camp Hill, Pa., assignor to Aircraft-Marine Products Inc., Harrisburg, Pa.

Application October 16, 1947, Serial No. 780,117

This invention relates to electrical connectors and connections and to the method of makin the same. More particularly the invention re-, lates to connectors which are crimped onto cables or wires and to the resulting electrical connection with a wire or a plurality of wires or other electrical connectors, and the method of making such electrical connection.

An object of this invention is to provide electrical'connectors and connections which avoid the difliculties of the prior art. A further ob ject is to provide electrical terminals which are inexpensive to manufacture and to apply, and which are dependable and efiicient in use. Another object is to connect insulated wires by connectors of the type which pierce the insulation to make a permanent and permanently low resistance connection with the central conductor, and at the same time grip the wire with a, high mechanical strength.

In the past iron which is used broadly to include steel has been considered unsuitable for electrical connectors except for low grade circuits where wide variations in the contact resistance are unimportant; and in fact, the Underwriters Laboratories, Inc. has had a ruling against the approval of iron connectors. The conductivity of iron is low as compared with copper; it is subject to corrosion or rusting and the rusted surfaces give very poor conductivity so that the contact resistance increases appreciably. In the field of crimped (i. e., pressureformed connectors) steel has been particularly avoided because its physical properties have been considered unsuitable for making absolutely tight pressure connections with copper wire by simple compression between the dies which are moved together, and also unsuitable formaintaining such pressure contact'after release from the dies. Steel has been considered too hard to form itself to the copper wire so as to give a. connection so tight as tomaintain good electrical contact with long life and so as to keep corrosion away from the contact areas. been generally believed that only copper and brass could be so effectively crimped without such spring-back as would impair the electrical contact. 7 r

In the copending application of James C.

'M'acy, Serial No. 679,630, filed June 27, 1946,

now Patent 2,557,126, issued June 9, 1951, there is disclosed a terminal structure and a mode 'of attaching the same to an insulated or uninsulated cable or wire. That terminal structure is'ideally suited for attachment to the un- It has 7 1 Claim. (Cl. 173-269) stripped end of an insulated cable. The terminals of the same general character as those disclosed in that Macy application are highly advantageous for use with the present inven tion, and will therefore be used as the illustrative embodiment in the following description. In accordance with the present invention these terminals are constructed of iron, such as soft low-carbon steel. The steel of these terminals, however, is given a low contact resistancerand extraordinary high stability of resistance by first coating the steel with a metal wet by mercury, especially a metal such as. copper which is read-i ily wet, but not amalgamated, and then apply-' ing' a coating of mercury and over it a metal such as tin, which does readily amalgamate with an excess of mercury. This coatingis advantageously applied in accordance with the methods disclosed in the, application of Annie G. Asaff, Serial No. 551,141, filed August 25,1944, now abandoned. The mercury and tin may be applied separately or they may be applied together in the form of an amalgam. In any event there ismercury present in the coating in 6X71; cess of that which will combine with the tin; so that the free mercury creeps along any uncoated metal surfaces in which the terminal comes in contact. v

The thin amalgam layer being plastic readily forms itself to the uninsulated surface configuration of thewire. If there is spring-back tending to open crevices between the wire and the connector, themercury soft plastic amalgam remains in them merely drawing in from larger masses which have been extrudedduring crimping. v

The present invention is not limited to terminals of the type disclosed in that Macy appli-,'

cation, but on the contrary the present inven-v tion contemplates constructing many different types of electrical terminals of sheet steel. The invention has particular advantage with the insulation piercing connectors shown and the connections made therewith, but it is applicable also to other types of crimped connectors and connections, for example as shown in U. S. Patent Nos. 2,379,567 and 2,359,083. The particular surface treatment of the steel as referred to above has outstanding advantages, including the fact that it insures good electri cal contacts; and also it prevents corrosion even upon surfaces which are not initially covered.

Prior to this invention connectors have been made in the form of strips ea-ch'comprising asuccession of blanks or terminals, partially;

formed, such as terminals which are completely formed except for the cutting apart and applying to the wire. One such strip is shown in Patent No. 2,396,913. These strips are fed to a terminal-applying tool or press which cuts each terminal free and applies it to the end of a wire.

In this specification and the accompanying drawing, 1' have shown and described a preferred embodiment of my invention and suggested various modifications thereof; but it is to be understood that these are not intended to be exhaustive nor limiting of the invention, but on the contrary, are given for purposes of illustration in order that others skilled in the art may fully understand the invention andthe principles thereof and the manner of applying it in practical use so that they may modify and adapt it in vari ous forms, each as may be best suited to the conditions of a particular use.

In the drawing:

Figure 1 is a top plan view of one complete terminal blank which constitutes onee'mbodiment of the invention, together with the end of the strip from which this terminal has been cut;

Figure 2 is a side elevation of the terminal blank of Figure 1 after it has been formed into a terminal;

Figure 3'is a perspective view of the terminal of Figure; 2 after being crimped to the end of an insulated wire;

Figures 4 to '7, inclusive, are sectional views whicl'iillustrate the crimping operations whereby the terminal of Figure 2 is crimped; to an insulated' wire; and,

Figure 8 is a plan view of a strip of terminal blanks constituting another embodiment of the invention.

Referring' particularly to Figure 1 of the drawin'g, there'i's shown a terminal blank 2 which has just been cut from the continuou strip indicated at 4'. At each end: of blank 2 there is an intervening" piece 6 which facilitates the cutting of the terminal blank from the strip without moving the blank from the plane of the strip. At the left pieceB is shown out free and this constitutes waste material, and at the right piece 6 is shown connected to the end of the strip. Blank 2 has a connecting portion 8, a ferrule portion Ill, and three ears [-2, I' l and I6.

Referring now to Figure 2 wherein the terminal blank isshown formed into a terminal, the ferrule portion Hf is substantially semi-cylindrical and the ears project upwardly from the longitudinal edges of this semi-cylindrical portion and have their free upper ends turned somewhat inwardly toward each other. The terminal in this form may be attached by crimping to an unstripped end of a wire such as wire I8 of Figure 3 which has a core 20 of multi-stranded wire and insulation H.

The attachment of the terminal to the wire is by a crimping operation best understood by referring'to Figures 4 to 7. Thus, in Figure 4, the terminal of Figure 2 having the end of a wire I8 therein is positioned on a die or anvil 2 8 which has associated with it a curling die 26'. As the dies move together, as illustrated in Figures 4' to '7', ear I? shown at the left rides in a spiral or cylindrical forming face having a surface 28' extending to the right and" thence downwardly; and ear Iii rides in a similarly shaped face 3!! extending to the left and thence downwardly; ear I (which does not show in- Figure 4, but which is positioned directly behind e'ar I2) rides in a face 32' (shown in broken lines) which extends to the right and thence downwardly. Die 26 moves downwardly relative to die 24 to the position shown in Figure '7, so that the ears are crimped in accordance with the showing of Figures 5, 6 and '7.

Thus, as pointed out more fully in the abovementioned Macy application, ears I2 and I6 pierce the insulation and the stranded core so that they grasp the central portion of the core very tightly. As shown in Figure 7, ear I2 has its curled end embedded in or curled around the stranded core and the ear is formed into substantially a spiral. At the left, the base of the ear and adjacent section of the ferrule portion I0 form a C-clamp which is somewhat thickened by the crimping operation, and which provides a rigid clamp holding the ear in its clamping position. Ear I6 is similarl curled from the other side of the ferrule portion Ii (see Figure 3). Surface 32 is so shaped that ear I4 is curled around the outside of insulation 22' so that it forms with ferrule portion ID a substantially cylindrical portion clamping the outside of the wire. Therefore, the terminal is clamped rigidly to the wire and good electrical contacts are provided by ears I 2 and I5.

In Figure 8 there is shown another embodiment of the invention, a terminal strip, generally indicated at 26, is cut as indicated at 38 by broken lines, into terminal blanks 40. These terminal blanks are formed into terminals similar to terminal 2 of Figures 1 to 7 and are attached to wires in a similar manner.

As pointed out above, the terminals of the illustrative embodiment are formed of soft steel which is plated with copper and coated with mercury and tin in accordance with the disclosure of the Asaff application, but prior to the coating the strips are blanked out to the configurations shown respectively in Figures 1 and 8. Thus all of the exposed surfaces of the strip are coated.

The steel terminals of the present invention are superior in many respects and for many uses to similar terminals made of copper or brass. For example, for terminals which must pierce insulation, the terminals of this invention are much superior to those made of copper or brass.

An annealed, soft, low-carbon steel is advantageously used in the practice of this invention. The high strength and high modulus of elasticity of such steel as compared with copper, for example, permits the use of thin and narrow piercing prongs or ears on the terminal with ends sharp enough to easily pierce the insulation and make good contact with the wire core. The desirable characteristics referred to above avoid the tendency of the ears to crimple or squat down before effectively piercing the wire. The relatively low yield point and low limit of elasticity of such annealed soft steel make it possible to crimp the connectors with the proper deformation and to assure when once crimped that the terminal will maintain the tightly crimped condition even under relatively severe stress.

For certain types of terminals I have obtained very satisfactory results with steel strapping which is a steel of the character referred to above. Specifically, steel having the designation of SAE 1010 is ideal for certain uses. However, the high degree of uniformity which is obtainable in steel or iron makes it possible to obtain a steel or iron which is ideally suited for each particular type of terminal. In this regard, the terms steel and iron are used inthe broader sense with it being understood that the term steel includes iron which is substantially free of carbon,

With terminals such as those shown in the drawing, it is important that the metal be sufficiently soft in the ferrule portion of the terminal to permit it to be compressed in the final stage of crimping, but yet the metal must be stiff enough to transmit the compressive forces without buckling. Furthermore, the metal at the side of the crimped ferrule is thickened during the crimping operation, thus limiting the springback so that the crimped terminal will maintain, as closely as possible, the extreme crimped condition which it reaches during the maximum extent of the crimping operation. In addition to this the ferrule must be thickened so as to give greater rigidity to each C-clamp section, which is the C-shaped section of the terminal including the side and bottom of the ferrule portion and the ear which exerts the main gripping force. The thickening and curling of the metal also involves work-hardening so that the crimped ferrule has increased rigi Steel has the further advantage over copper that it will not slowly yield to a maintained force, but on the contrary holds the compressive force; whereas, copper cold flows slowly under like forces before they reach an equilibrium condition, and during this cold flow the compressive force may be relieved to some extent so that the crimp is somewhat loosened.

The steel from which the connectors of the type shown in the drawing are made, must have compressive strength sufficient to overcome its resistance to bending on the radius of the curling die faces 28, 30 and 32 which is approximately one-third, of the width of the ferrule, plus its resistance to sliding in the die. However, this compressive strength must be low enough to obtain plastic flow by compression in the walls of the ferrule portion during the final closing together of the crimping dies; in this way the ferrule portion and the wire are deformed simultaneously. This gives considerable latitude for any particular application because the relative amounts of deformation of the ferrule portion and the wire need not be maintained within close limits. That is, with a terminal of soft steel on a relatively hard wire, there may be more deformation in the sides and ears of the crimped sults obtained with each of these terminals areextremely satisfactory for use under specific conditions.

While the present invention is disclosed in connection with insulation-piercing terminals it is to be understood that some of the advantages of the invention can be realized with other and different types of connectors.

From the foregoing it will be seen that an electrical connector made in accordance with the present invention is well adapted to attain the ends and objects hereinbefore set forth and to be economically manufactured since the whole combination is suited to common production methods and is susceptible to a wide latitude of variations as may be desirable in adapting the invention to different applications.

I claim:

An electrical connector of the insulation piercing type comprising a base of soft steel, a plating of copper over said steel and a mercury-tin amalgam on said copper.

FRANK L. PIERCE.

REFERENCES CVITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,067,702 Weigand July 15, 1913 1,070,948 Dodd Aug. 19, 1913' 1,309,887 Fulton July 15, 1919 1,648,605 Bobo Nov. 8, 1927 1,949,623 Quarnstrom Mar. 6, 1934 1,959,150 Basch May 15, 1934 2,038,535 Brenizer Apr. 28, 1936 2,302,767 I-Iackbarth Nov. 24, 1942 2,410,321 Watts Oct. 29, 1946 2,557,126 Macy June 19, 1951 FOREIGN PATENTS Number Country Date 1 2,399 Great Britain of 1865 3,299 Great Britain 1865 66,983 Austria 1 of 1914 

